Researchers at Technical University of Munich have developed a novel PET imaging technique that enables clinicians to visualize engineered CAR-T cells within the body. The method involves inserting an artificial receptor into CAR-T cells and administering a specialized radioactive tracer that binds exclusively to these cells, allowing precise tracking via PET scans. This advance promises to help clinicians monitor CAR-T cell distribution, proliferation, and potential off-target effects, addressing a critical gap in understanding therapeutic cell dynamics. Built on decades of protein engineering work on anticalins, this approach offers a non-toxic, highly specific modality for enhancing the safety and efficacy of adoptive cell therapies.